OK so I got my 94 Blazer running today, and went to charge the AC. It is acting very odd, like nothing I have seen before. It will run perfect for about 3-4 min, nice and cold and the PSI on the low side gets down to about 35. Then the compressor turns off for a full 4-5 min, and the pressure on the low side only creaps up to about 70-75 and then the compressor comes back on. I do not have a gauge set, just the cheap gauge that comes on the R134 can. Any one have and Ideas as to what the problem can be?
Sounds like the pressures are doing as they should with the conditions you’re describing. When the compressor is running, the low side should drop as you noticed, and the high side pressure will go up. When the compressor shuts down, the pressures will slowly equalize, with the low side going up and the high side going down.
The question is, why is the compressor shutting down? There are two safety switches on this system. There is a low pressure safety switch which will cut the compressor if the low side gets too low. There is also a high side pressure switch, which will cut the compressor if the high side goes too high. To determine the problem, a full set of gauges will need to be hooked-up and analyzed.